The present disclosure is generally directed to toner processes, and more specifically, to the aggregation and coalescence of an aqueous suspension of colorant, such as pigment particles, wax particles and resin particles, utilizing a coagulant to afford toner composites of various suitable sizes, such as for example, from about 1 to about 15, and preferably from about 3 to about 11. More specifically, disclosed in embodiments is the preparation of an ultra low melt polyester based chemical toners, comprised of a colorant, optionally a wax, an amorphous resin and a crystalline resin, and wherein the process allows for minimal or no plasticization of the amorphous and crystalline resin such that excellent heat cohesion or blocking, such as from about 52° C. to about 60° C., is obtained, and excellent tribocharge, charge maintainability, and relative humidity (RH) sensitivity results, where the low melt or ultra low melt fixing temperature is, for example, from about 100° C. to about 130° C. Further, disclosed is a toner process comprising the aggregation and coalescence of an amorphous polyester, a crystalline polyester and a colorant, and wherein the coalescence is conducted at a temperature that is lower than the melting point temperature of the crystalline polyester, resulting in toners that are low melting with excellent resistivity, low melting characteristics, and where migration of the crystalline polyester to the toner surface is substantially avoided or minimized, and in embodiments a narrow GSD of, for example, from about 1.16 to about 1.26, or about 1.18 to about 1.28, as measured on the Coulter Counter, can be obtained. The toner process disclosed in embodiments enables the utilization of polymers such as polyesters obtained by polycondensation reactions. The resulting toners can be selected for known electrophotographic imaging methods, printing processes, including color processes, digital methods, and lithography.
Also included within the scope of the present disclosure are methods of imaging and printing with the toners illustrated herein. These methods generally involve the formation of an electrostatic latent image on an imaging member, followed by developing the image with a toner composition comprised, for example, of thermoplastic resin, colorant, such as pigment, wax, charge additive, and surface additive, reference U.S. Pat. Nos. 4,560,635; 4,298,697 and 4,338,390, the disclosures of which are totally incorporated herein by reference, subsequently transferring the image to a suitable substrate, and permanently affixing the image thereto. In those environments wherein toner is to be used in a printing mode, the imaging method involves the same operation with the exception that exposure can be accomplished with a laser device or image bar. More specifically, the emulsion aggregation coalescent toners disclosed herein can be selected for the Xerox Corporation iGEN® machines that generate with some versions over 100 copies per minute. Processes of imaging, especially xerographic imaging and printing, including digital, and/or color printing, are thus encompassed by the present disclosure. Moreover, the toners of this disclosure are useful in color xerographic applications, particularly high-speed color copying and printing processes.
Emulsion/aggregation/coalescing processes for the preparation of toners are illustrated in a number of Xerox patents, the disclosures of which are totally incorporated herein by reference, such as U.S. Pat. Nos. 5,290,654, 5,278,020, 5,308,734, 5,370,963, 5,344,738, 5,403,693, 5,418,108, 5,364,729, and U.S. Pat. No. 5,346,797. Also of interest may be U.S. Pat. Nos. 5,348,832; 5,405,728; 5,366,841; 5,496,676; 5,527,658; 5,585,215; 5,650,255; 5,650,256; 5,501,935; 5,723,253; 5,744,520; 5,763,133; 5,766,818; 5,747,215; 5,827,633; 5,853,944; 5,804,349; 5,840,462; 5,869,215; 5,910,387; 5,919,595; 5,916,725; 5,902,710; 5,863,698, 5,925,488; 5,977,210 and 5,858,601. The appropriate processes and components of these patents may be selected for the present disclosure in embodiments thereof.
Two main types of emulsion aggregation (or EA) toners are known, reference for example a number of the Xerox Corporation emulsion aggregation U.S. patents recited herein, and more specifically, U.S. Pat. No. 6,120,967, the disclosure of which is totally incorporated herein by reference, and U.S. Pat. No. 5,916,725, the disclosure of which is totally incorporated herein by reference.
Emulsion aggregation techniques typically involve the formation of an emulsion latex of the resin particles, which particles have a small size of from, for example, about 5 to about 500 nanometers in diameter, by heating the resin, optionally with solvent if needed, in water, or by preparing a latex in water. A colorant dispersion, for example comprised of a pigment dispersed in water, optionally also with additional resin, is separately formed. The colorant dispersion is added to the emulsion latex mixture, and an aggregating agent or complexing agent is then typically added to initiate aggregation of larger size toner particles. Once the desired size toner particles are achieved, aggregation is stopped. The aggregated toner particles may then be heated to enable coalescence/fusing, thereby achieving aggregated, fused toner particles.
Low temperature fixing toners comprised of semicrystalline resins are known, such as those disclosed in U.S. Pat. No. 5,166,026, the disclosure of which is totally incorporated herein by reference, and which toners are comprised of a semicrystalline copolymer resin, such as a poly(alpha-olefin) copolymer resin, with a melting point of from about 30° C. to about 100° C., and containing functional groups comprising hydroxy, carboxy, amino, amido, ammonium or halo, and pigment particles. Similarly, in U.S. Pat. No. 4,952,477, the disclosure of which is totally incorporated herein by reference, toner compositions comprised of resin particles selected from the group consisting of a semicrystalline polyolefin and copolymers thereof with a melting point of from about 50° C. to about 100° C. and pigment particles are disclosed. In U.S. Pat. No. 6,413,691, the disclosure of which is totally incorporated herein by reference, there is illustrated a toner comprised of a binder resin and a colorant, the binder resin with a crystalline polyester containing a carboxylic acid of two or more valences having a sulfonic acid group as a monomer component, and which toners usually possess a narrow fusing latitude, and thus are inferior for contact fusing applications wherein high gloss images are desired. Furthermore, crystalline resins are typically of a low resistivity thus resulting in poor tribocharge, unacceptable charge maintainability, and high RH sensitivity.
Low fixing toners comprised of crystalline resin and amorphous polyester resin are illustrated in U.S. Pat. Nos. 5,147,747; 5,057,392; 7,115,350; 7,056,635; 6,942,951; 6,890,695; 6,383,705, and 6,780,557, the disclosures of which are totally incorporated herein by reference,.
Also, polyester based emulsion aggregation toners comprised of a crystalline and an amorphous resin are known, such as the sulfopolyester based toners of U.S. Pat. No. 6,830,860, the disclosure of which totally incorporated herein with reference. The toner and process of U.S. Pat. No. 6,830,860 are comprised of sulfonated polyester resin, and which toner can in a number of instances have a poor resistivity and undesirable triboelectric charging at certain relative humidities, mainly due to the hydrophilic nature of the sulfonated moieties.
There is thus a need for a low fixing toner, such as from about 100° C. to about 130° C., comprised of an amorphous and crystalline resin, and wherein such toner is prepared by an economical process, such as emulsion aggregation, and such that small particle sizes, such as from about 3 to about 9 microns, and more specifically, from about 4 to about 7 microns, are obtained for high resolution color applications, and wherein these toners exhibit broad fusing latitude of from about 50° C. to about 90° C., excellent print quality, high gloss, and stable xerographic charging in ambient environments for substantially all colors with a low RH sensitivity, such as from about 0.5 to about 1, and a high toner glass transition temperature, such as from about 55° C. to about 60° C. with low heat cohesion at 55° C., such as from about 1 to about 20 percent flowability.